dojo.connect

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dojo.connect connects events to methods, so that after the event occurs, the new connected method is called too.

Introduction

dojo.connect is the core event handling and delegation method in Dojo. It allows one function to "listen in" on the execution of any other, triggering the second whenever the first is called. Many listeners may be attached to a function, and source functions may be either regular function calls or DOM events.

dojo.connect connects listeners to actions, so that after event fires, a listener is called with the same arguments passed to the orginal function.

Since dojo.connect allows the source of events to be either a "regular" JavaScript function or a DOM event, it provides a uniform interface for listening to all the types of events that an application is likely to deal with though a single, unified interface. DOM programmers may want to think of it as "addEventListener for everything and anything".

When setting up a connection, the event parameter must be a string that is the name of the method/event to be listened for. If obj is null, dojo.global is assumed, meaning that connections to global methods are supported but also that you may inadvertantly connect to a global by passing an incorrect object name or invalid reference.

dojo.connect generally is forgiving. If you pass the name of a function or method that does not yet exist on obj, connect will not fail, but will instead set up a stub method. Similarly, null arguments may simply be omitted such that fewer than 4 arguments may be required to set up a connection See the examples for deails.

The return value is a handle that is needed to remove this connection with dojo.disconnect.

Usage

dojo.connect(obj, event, context, method, dontFix);
Parameter Type Description
obj Object|null The source object for the event function. Defaults to dojo.global if null. If obj is a DOM node, the connection is delegated to the DOM event manager (unless dontFix is true).
event String name of the event function in obj. I.e. identifies a property obj[event].
context Object|null The object that method will receive as "this". If context is null and method is a function, then method inherits the context of event. If method is a string then context must be the source object object for method (context[method]). If context is null, dojo.global is used.
method String|Function A function reference, or name of a function in context. The function identified by method fires after event does. method receives the same arguments as the event. See context argument comments for information on method's scope.
dontFix Boolean Optional. If obj is a DOM node, set dontFix to true to prevent delegation of this connection to the DOM event manager.

Examples

// When obj.onchange(), do ui.update():
dojo.connect(obj, "onchange", ui, "update");
dojo.connect(obj, "onchange", ui, ui.update); // same
// Using return value for disconnect:
var link = dojo.connect(obj, "onchange", ui, "update");
...
dojo.disconnect(link);
// When onglobalevent executes, watcher.handler is invoked:
dojo.connect(null, "onglobalevent", watcher, "handler");
// When ob.onCustomEvent executes, customEventHandler is invoked:
dojo.connect(ob, "onCustomEvent", null, "customEventHandler");
dojo.connect(ob, "onCustomEvent", "customEventHandler"); // same
// When ob.onCustomEvent executes, customEventHandler is invoked
// with the same scope (this):
dojo.connect(ob, "onCustomEvent", null, customEventHandler);
dojo.connect(ob, "onCustomEvent", customEventHandler); // same
// When globalEvent executes, globalHandler is invoked
// with the same scope (this):
dojo.connect(null, "globalEvent", null, globalHandler);
dojo.connect("globalEvent", globalHandler); // same

dojo/connect (last edited 2009-12-19 04:33:18 by MarcusReimann)